is this a manual or automatic transmission i dont know jack about old celicas so do you know if yours has a limited slip diff to answer your question no transmission fluid which is what youd call automatic transmission fluid and diff oil are not the same thing however if were talking manual transmission youd use gear oil and in most applications you can use the same oil in a manual tranny and a differential but like others have said read your manual itll tell you what fluids to use in each device